Yet another research report shows booming sales of Android smartphones: NPD, which covers the retail market, says that 33 percent of smartphones sold in the US in the second quarter ran Google’s operating system. RIM’s BlackBerries fell to second place, at 28 percent, and Apple’s iPhones had 22 percent of the market.

NPD’s analysis covers only phones, so there are millions of Apple iOS devices–iPod Touches and iPads–that aren’t part of the tally. Except for a few niche products such as Archos’s tablets and the Nook, Android is still a phone OS, not a general-purpose one; that will change in the months to come as Android tablets (and products such as Google TV) arrive.

Each company that does this sort of number-crunching uses its own methodology, and sales patterns for the rest of the world differ wildly from those for the US. So it’s not surprising that different companies are releasing varying rankings. After the jump, a quick visual recap of some recent stats.